1. Field of the Invention
Aspects of this invention relate generally to printers, and more particularly to printers configured for printing coding or tracking information on an egg carton.
2. Description of Related Art
By way of background, printing of coding or tracking information on egg cartons is known, as such is required for traceability and per FDA requirements and the like. However, current egg carton printing techniques are deficient in a number of respects. First, and currently the most common arrangement, is a mechanical stamper, or reciprocating ink printer or pad printer. Such a printer requires that the print substrate (in this case the egg carton) be stationary and so is typically installed adjacent the “egg drop” area of the egg carton filling line, where the carton would be mechanically indexed and held in place by a stabilizing arm, thereby ensuring that each carton is always in the same position for the egg drop, and thus for printing as well at that same station. But such stampers or pad printers have a number of shortcomings. Due to the fact that the mechanical printers use metallic type sets, variable printing (i.e., real-time printing with date, time, etc.), which is required for better traceability and recall, is not possible. In other words, mechanical printing offers only fixed or limited message printing which doesn't serve the purpose of date coding for improved traceability and to limit any expensive recalls to a specific affected batch, plant, production line, window of production time, etc. Also, mechanical stampers require relatively constant and expensive manual intervention in changing the type sets, inking the pad, etc. Thus, while mechanical stampers offer relatively consistent print quality, they are not readily adapted to changing lot/batch coding information. And when it is considered that the average egg farm has 60 to 120 such printers, it will be appreciated that manually changing the pad printer type set information to update the date or other batch information would be quite cumbersome and so is simply not done that often, providing less effective traceability (e.g. to a whole week or span of days versus true, robust, real-time traceability).
As such, thermal ink jet, continuous ink jet, and drop-on-demand print technologies have made their way into the egg carton printing context as an alternative to mechanical stampers. However, these printers have shortcomings as well. With such printers, the distance from the printhead to the substrate is very critical to ensure a good quality print. The distance has to be substantially constant in order for the ink drops ejected from the printer to be placed in the right locations on a moving object. As such, two parameters that determine accuracy and clarity in ink jet printing are the speed and the distance. If the product or print substrate is moving at a constant speed and at a constant distance (specified) from the printhead, one could potentially have a good print, assuming the right ink for the substrate as well. But specific to egg cartons, trying to print on a moving carton is a very big challenge. There are basically two opportunities or options to print a moving carton in the typical egg carton fill line and both present significant difficulties and significantly compromise reliability and functionality. Again, all such ink jet printing technologies rely on relative movement between the printhead and the print substrate. So, in the egg carton printing context, such ink jet printers have been employed either before the egg drop once the empty cartons are de-nested and put on a conveyer delivering them to the egg drop or after the egg drop as part of the take-away conveyor. Once again, though, each such approach presents challenges and deficiencies in practice. First, regarding the de-nested, empty cartons on the delivery conveyor ahead of the egg drop, it will be appreciated that the cartons, whether made of cardboard, pulp, foam, or PET, are very light and so would normally tend to be skewed when they are de-nested, as the cartons are really not positively located or indexed until they enter the egg drop section. As such, the light weight cartons do not allow alignment or presentation of the empty cartons at a uniform distance from the printhead, creating problems for print quality. The other option employed to this point is to place an ink jet printer along the take-away conveyor. There, the cartons are at least weighed down a bit by the eggs now in them and coming out of the egg drop are more consistently aligned on the conveyor. But in addition to there still remaining concerns even along the take-away conveyor of the cartons either being askew or otherwise not at a consistent distance from the printhead as they pass by, there is also the possible issue of a carton not being closed properly and the eggs themselves, rather than the carton, being printed on, at least in part. With either approach—printing before or after the egg drop—there are also issues that arise since the speed of the carton likely is variable, such that it may become necessary to have an expensive encoder system to detect the speed of the carton and/or conveyor and relate it to the printer to ensure print placement relative to the carton. Also, if barcode printing (2D) becomes necessary or is desired, printing on the de-nester or takeaway conveyor without accurate alignment of the carton and constant speed (or an encoder system to monitor and account for speed variance) would not be possible.
Finally, in view of the foregoing challenges and shortcomings of each printing option, it would seem that a variable printing mechanical printer would be ideal, but such a system is effectively cost prohibitive and significantly limits the printing speed.
As such, it will be appreciated that all known egg carton printing approaches employed to date have one or more shortcomings. Accordingly, aspects of the present invention fulfill these needs and provide further related advantages as described in the following disclosure.